A stagnation-point flow burner facility has been developed to provide a canonical framework to study the catalytic surface reactions of premixed combustion systems. The configuration serves as an important platform to investigate the interaction between homogeneous and heterogeneous reactions with an independent control of the characteristic residence time scales. Methane/air, and propane/air mixtures were examined with or without the presence of a platinum catalyst located at the stagnation surface. The effects of oxidizer composition and nitrogen dilution were examined. Depending on the operating conditions, either a stable gas-phase flame is established between the nozzle and the stagnation surface or the unburned reactant mixture directly impinges on the heated surface. In the former case, the extinction limits of the gas-phase flame were measured for various equivalence ratios and flow conditions. In the latter case, the heat release resulting from the surface reaction was quantified by measuring the surface temperature of the stagnation plate. The results are discussed in terms of the relative contributions of the gas-phase and the surface reaction chemistry to the burner performance. Understanding gained from this study will provide insights into the role of catalytic reactions in extending the flammability of compact combustors subjected to excessive surface heat loss.

Recent advances in PEM fuel cell systems have demonstrated their role in the production of clean and efficient power. However, due to complexities and safety concerns in the storage and transport of hydrogen, development of on-board fuel processing of hydrocarbon into hydrogen is being considered a critical issue in the success of the fuel cell technology in transportation application. In this paper, a novel concept of scalable silicon micro-reactor with an integrated platinum heater is developed for preferential CO oxidation. The performance of the micro-reactor is assessed and compared to a packed-bed reactor model. Complementary experimental and modeling efforts are made to identify the optimal thermal design parameters. It is demonstrated that the silicon micro-reactors successfully achieves the objectives of scalability without suffering from loss of efficiency due to the mass transfer limitations.

Recent progress in the fuel cell technology has attracted research interests in providing hydrogen in a safe and efficient manner. One of viable approaches is to develop on-board catalytic fuel processors which converts higher hydrocarbon fuels into hydrogen. While this is a promising method and the level of catalytic material development is mature, the compact fuel processor system suffers from relatively low efficiency primarily due to the large surface-to-volume ratio causing excessive heat loss to the ambient. In this paper, a systematic modeling approach is presented as an effective tool to undertake extensive parametric study to identify crucial design parameters to accomplish optimal thermal management of the fuel processor system. By adopting a canonical counterflow heat exchanger system, effects of key system parameters, such as reactant and control flow rates, and inlet temperatures, on the system efficiency, conversion, and reactive length are investigated. The model is applied to a partial oxidation reactor and results are discussed.

Micro-scale combustion is an attractive alternative as a power source for numerous applications. The high-energy densities of hydrocarbon fuels make micro-scale combustors particularly appealing in comparison to fuel cells, batteries and other power generation devices. One of the major difficulties in the development of a micro-scale reactor is to sustain stable combustion in a small device with a high surface-to-volume ratio. To this end, catalytic combustion is considered a viable means to extend the operating range of combustors. In this work, a new stagnation-point flow burner facility has been developed to provide a canonical framework to study the interactions between fluid dynamics and chemical reactions in the gas-phase and heterogeneous modes. The stagnation-point flow burner is used to study extinction limits of catalyst-assisted premixed methane combustion. Basic characterization of the burner is performed and preliminary experimental data for extinction limits are presented as a function of the flow strain rate, mixture equivalence ratio, and the level of catalytic activity.